The present invention is related to a method for adjustment of the control current of current-controlled hydraulic valves for the actuation of individual hydraulic functions of industrial trucks, according to the preamble of patent claim 1.
With industrial trucks it is known to actuate a number of functions in a hydraulic manner. To these belong the lifting and lowering of a hoisting device, the displacement of a lifting bench in a reach mast truck, the tilting of the lifting bench and, occasionally, the displacement of the hoisting device in a lateral direction. To each function belongs at least one hydraulic adjustment cylinder, and the triggering of the adjustment cylinder takes place with the aid of a hydraulic valve. Upon opening of the valve, the actuated part moves with a predetermined speed, which of course, a predetermined pressure being assumed, depends upon the opening cross section. As is well known, the opening cross section of the valve is adjusted by a pre-controlling device, e.g. an electromagnet. Thus, the control current at the electromagnet determines the effective cross section.
According to lifting height, vehicle type and so on, the speed at which the hydraulically actuated part is moved has to be adjusted in an appropriate manner. The control current for the respective valves is generated with the aid of an electronic control device, which on its part receives a transmitter signal from an operator's control or the like, which is manually actuated, e.g. By reason of not avoidable work tolerances, different function speeds result on the valve at a predetermined control current. It is therefore known to calibrate each valve before it is brought to operation, with the aid of an on-board computer of the industrial truck. The control current for the triggering of the electromagnet is manually corrected. Such a procedure is time-consuming and can result in incorrect adjustments.
The invention has therefore the objective to specify a method for the adjustment of the control current of current-controlled hydraulic valves for the actuation of individual hydraulic functions of industrial trucks, which can be performed more rapidly and more simply.